Transmitter circuit arrangement



. Oct. 27, 1936. w. KUMMERER Y 2,058,999

TRANSMITTER C IRCUIT ARRANGEMENT Fild Dec. 17, 1932 2 Sheets-Sheefc 1INVENTOR W/LHELM-KUMMFRl-R '7 BY Y ATTORNEY Oct. 27, 1936. w. KUMMERER2,058,999

fl'BANSMITTER CIRCUIT ARRANGEMENT 7 Filed Dec. 17, 1932 Z-Sheets-Sheet 2Azrskur/m INVENTOR W/L HELM KUMMEKH? A'ITORNEY Patented Oct. 27 l UNITEDSTATES PATENT OFFICE TRANSMITTER CIRCUIT ARRANGEMENT tion of GermanyApplication December 17, 1932, Serial No. 647,721 In Germany December29, 1931 8 Claims.

The increasingly severer conditions of modern amplifier and transmitterconstruction as regards the avoidance of non-linear distortionnecessitate the adoption of special arrangements and schemes. Thepresent invention relates to amplifiers which include counter-couplingor compensating coupler schemes.

The novel features of the invention have been pointed out withparticularity in the claims attached hereto.

The invention, however, as to nature and operation, will be described indetail. In such description reference will be made to the drawings, inwhich:

Figures 1 and 2 show tube characteristics which aid in the disclosure ofthe invention; while,

Figures 3 to '7 inclusive show different modifications of an amplifierconstructed in accordance with my invention.

Referring to the drawings, Figure 1 shows a tube characteristic, thelower end of which is idealized as-to form. The tube shall be supposedto work as an amplifier of the class B type, for instance, exactly atthe bottom knee, that is, at the lower end of the straight line portionof the curve The fundamental harmonic of the ensuing alternatingcurrent, upon application of a' sinuous alternating gridpotential, willthen be proportional-to-the latter as long as the tubeis operating inthe rectilinear part of its characteristic curve. The assumption shallbe made that the active grid potential is composed of the difference ofa potential which'is linearly variable With respect to the signallingWave or current to be amplified and an oppositely acting potential oflower absolute valuewhich is proportional to the amplified currentof'fundamental frequency or a harmonic thereof. Now, as long as theresultant potential stays in the rectilinear part of the characteristic,the impressed and the oppositely coupled potential will always bepro-'portional to each other, in other words, the generated currentincreases linearly with increase in the amplification of the appliedpotential, though at a less rapid rate than is true in the absence ofcounter coupling. But as soon as the resultant voltage comes to bewithin the lower portion of the upper knee of the characteristic theapplied current no longer will increase linearly, hence, also thecounter potentialwill decrease or increase less rapidly with theconsequence that the resultant alternating grid voltwhere the countercoupling is absent; the ensuing current therefore is larger, and theshape of the current comes closer to a linear condition than is true inthe absence of counter coupling. This consideration, as will beunderstood, holds, of course, true also of the reversed behavior in thelower knee and also for amplitude-dependent external resistance (forinstance, grid circuits for which the damping is variable as a result ofnon-linearity of the grid direct current). In graphic form the resultingimprovement can be clearly represented in the following manner: Platecurrent and impressed grid alternating voltage, in the absence ofcounter coupling, shall be denoted by i and e in the presence ofcountercoupling by i and c Suppose the countercoupling is egeg=k'7;',

then without counter-coupling i=Se and with counter-coupling i'=S(e 'eye=Se Ski'.

Examining the case of like resultant plate current, when i=1" then:

in other words, the grid alternating potential e to be impressed uponthe tube in the case of counter-coupling is equal to the original gridpotential e increased by the addition Expressed in graphical form thismeans nothing else than the shearing in an amount equal to the straightIn other Words, the characteristic curve is shifted and straightened outas shown in Figure 1 at i=f(6g). Now, it will be readily understood thatthe current curve for c should be less curved than in the case of eseeing that in the curved portion the value of e which no longer varieslinearly with linearly growing current, is joined merely additively tothe straight In other words, contrary to what might be thought at firstblush, the process does not involve a mere change in scale.

In order to make the resulting improvement still more conspicuous thecurrent-curves obtained are plotted in Figure 2 with changes in scale ofe in such a way that beginning and end coincide.

The advantages as regards properties of modulation, at least in the caseof radio frequency arrangements, can be effectively realized onlyprovided that in spite of the potential of the main circuit brought tothe grid, neutralization is maintained. This requirement fundamentallyis fulfilled by the simple bridge scheme in a capacitive gridneutralized arrangement as shown in Figure 3. It can be seen from theillustration quite readily that the plate potential by way of theinternal tube capacity between grid and plate and the resultant gridcathode capacity is divided by condensers NC and AC. Plate potential isimpressed with the same phase, i. e., in countercoupling sense, upon thegrid at point B by NC and on the other terminal of 2 by AC. The otherpoint of connection, A, of the inductance 2, on which the oscillationsfrom the pilot valve are impressed by I, looked at from the viewpoint ofthe master transmitter, owing to the voltage division by way of theneutralizing condenser NC and the other grid voltage divider condenserAC, receives the same voltage as the grid point B; in other words, noelectromotive force of the master valve oscillation circuit 4, 5 willproduce a current in the grid coupling coil, and the arrangementtherefore is neutralized. Since, at least for longer waves, voltagedivision by way of the internal tube capacity, because of the rotationof the grid phase by the active grid current, may not be expected toconduce to satisfactory results, the internal tube capacity, accordingto the invention, between grid and plate is raised by supplementarycapacities. In fact, in the limiting case, conditions in this respectmay be pushed to a point where the entire capacity of the oscillationcircuit is placed in the resultant grid plate or neutralizing capacityas indicated in Figure 4, wherein the capacity 5 has been omitted. Thisarrangement is otherwise the same as Figure 3.

Generally speaking, an inductive type of counter-coupling may bepreferable to the capacitytype where long waves are dealt with. A gridneutralizing scheme comprising an inductive counter-coupling is shown inFigure 5, in which the potential producing the counter-coupling effectis applied to bridge points in reference to the pilot transmitter by wayof winding 1 and impedances 2 as well as capacities AC and NC so thatneutralization is not disturbed.

In a similar manner also amplifiers with plate neutralization can beprovided with the countercoupling scheme without impairingneutralization. A number of exemplified embodiments are shown in Figures6 and 7. Here the capacity NC neutralizes the grid to plate capacity ofthe tube only. The additional driving effect is obtained by couplingwinding 4 by way of windings l and 9 to the winding I connected to thedivided input winding 2 in such a manner that the anode circuit 4,impresses no disturbing voltages on the pilot oscillator by way ofwinding 2. In the latter two instances, in order to restore the state offreedom from reaction impaired by the counter-coupling, a condenser CGmust be inserted, and this condenser, for instance, in the presence of avoltage divider ratio of 1:1 at the grid coupling coil must be equal tothe resultant grid-filament capacity of the master valve. What is heremeant by resultant grid-filament capacity is the capacity between gridand filament existent from the viewpoint of the pilot valve; in otherwords, firstly, the grid-filament capacity itself, and parallel theretothe series arrangement comprising the grid-plate capacity and uppervoltage divider and the series arrangement comprising the neutralizingcapacity and the lower voltage divider.

Having thus described my invention and the operation thereof, what Iclaim is:

1. Means for amplifying alternating currents comprising, a thermionictube having a control grid, an anode and a cathode, an alternatingcurrent circuit connected between said control grid and said cathode,which circuit includes an inductance which may be energized by thecurrents to be amplified, an alternating current circuit connectedbetween said anode and said cathode, said last named circuit being tunedby capacity to the frequency of the alternating currents to beamplified, a circuit for impressing potentials from said anode circuitto the control electrode of said tube, said circuit simultaneouslyimpressing said potentials on the terminal of the inductance in saidcontrol electrode cathode circuit connected with said control electrodeto offset potentials transferred through the impedance of said tube fromsaid anode to said control electrode, and means for compensating theeffect of said potentials applied from said output circuit to saidcontrol electrode and inductance terminal on the alternating currentflowing in said inductance including a circuit for transferringpotentials from said output circuit to the other terminal of saidinductance.

2. An arrangement as recited in claim 1 in which the potentials appliedfrom the output circuit to the control grid and simultaneously to theterminal of the inductance connected therewith are in phase with thepotentials applied from the output circuit to the other terminal of saidinductance.

3. An arrangement as recited in claim 1 in which the circuit fortransferring potentials from the output circuit of said thermionic tubeto the control grid and simultaneously to the terminal of the inductancein the input circuit connected with said control grid includes avariable capacity, and the circuit for transferring alternating currentpotentials from the anode and output circuit of said tube to the otherterminal of said inductance in said control grid cathode circuitincludes a variable capacity.

4. Signalling means comprising, a source of alternating currentpotentials, a thermionic tube, said tube having an anode, a cathode anda control electrode, an inductance connected between said controlelectrode and said cathode, said inductance being coupled to said sourceof alternating current, an output circuit connected between said anodeand said cathode, said output circuit being tuned by the capacity ofsaid tube to the frequency of the alternating current source, means forpreventing harmonic distortion in said circuit comprising, a circuitconnected between the anode of said tube and the control grid of saidtube to transfer potentials from the anode of said tube to the controlgrid of said tube, and means for preventing the potentials transferredfrom said anode to said control grid from reacting through saidinductance connected with said control grid on said source comprising, acircuit connected between the anode of said tube and the terminal ofsaid inductance remote from said control grid.

5. An arrangement as claimed in claim 4 in which said circuit connectedbetween said anode and said control grid and said circuit connectedbetween said anode and the terminal of said inductance remote from saidcontrol grid both include variable capacities.

6. Amplifying means comprising, a thermionic tube having an anode, acathode and a control grid, an inductance adapted to be energized byfrequencies to be amplified, a connection'between a point on saidinductance and the control grid of said tube, a connection betweenanother point on said inductance and the cathode of said tube, avariable capacity connecting the anode of said tube to the cathode ofsaid tube, a second inductance, a connection between a point on saidsecond inductance and the cathode of said tube, a connection between theanode of said tube and one terminal of said last named inductance, avariable capacity connecting a point on said last named inductance to apoint on said first named inductance, a neutralizing capacity connectedbetween the anode and control grid of said tube, and means for couplingthe first named inductance to the second named inductance.

7. A source of alternating current potentials and means for amplifyingthe potentials from said source comprising, a thermionic tube having ananode, a cathode and a control grid, an inductance connected betweensaid control grid and said cathode, said inductance being coupled tosaid source, a capacity connecting each terminal of said inductance tothe anode of said tube, a second inductance connected between the anodeand cathode of said tube, impedances connected with terminals of saidfirst named inductance, and an additional inductance connecting saidimpedances to the cathode of said tube, said additional inductance beingcoupled to said second named inductance.

8. Amplifying means comprising, a thermionic tube having anode, cathodeand control grid electrodes, an inductance adapted to be energized byalternating current potentials to be amplified, a connection between oneterminal of said inductance and the control grid of said tube, aconnection between a point on said inductance and the cathode of saidtube, said last named connection including a second inductance, a thirdinductance, said third inductance being coupled to said second namedinductance, a connection between a point on said third inductance andthe cathode of said tube, a connection between one terminal of saidthird inductance and the anode of said tube, said terminal also beingconnected to the control grid of said tube by way of a variablecapacity, and a connection between the other terminal of said thirdnamed inductance and the control grid of said tube, said last namedconnection also including a variable capacity.

WILHELM KUMMERER.

